This invention relates to a small telescopic or telephoto lens assembly having a brightness factor or f number of approximately 1:4 and a viewing field angle of less than 15 degrees.
In view of ease of operation considerations, the miniaturization of an interchangeable lens assembly for a 35 mm single lens reflex camera has a practical limit at a focal distance on the order of 200 mm. The present invention aims at the miniaturization of a telescopic lens assembly on this order, and a specific feature resides in the distance between the apex of the front lens and the image forming surface being less than 0.85 times the focal distance. This invention is a development or improvement of the invention disclosed in Japanese Patent Application Publication No. 3417/1968.